Apprehensions of illegal immigrants dropped dramatically in 2008, continuing a three-year decline attributed to the increase in Border Patrol surveillance and the poor U.S. economy, the Department of Homeland Security’s Office of Immigration Statistics said Tuesday.

The 2008 tally was 724,000, putting apprehensions at its lowest level since 1973.

While there were some coastal apprehensions made by Border Patrol, 97 percent of the captures were made on the Southwest border.

Statistics track apprehension events rather than numbers of individuals, who may be apprehended more than once.

In 2007, there were 876,803 apprehensions, compared to a mid-decade peak in 2005 of nearly 1.2 million and an all-time peak of nearly 1.7 million in 1986 as immigrants streamed across the border ahead of legislation granting amnesty.

Most of those picked up, 91 percent, were Mexicans with a sprinkling of immigrants coming from Central American and other countries.